About

Professor Seth Lichter is a faculty member in the Department of Mechanical Engineering at Northwestern University. His research focuses on dynamics on the molecular scale, with particular interest in how molecules diffuse over solid surfaces under shear. He emphasizes the development of simple analytical models and the derivation of closed-form approximate solutions, often tackling complex problems that are too large for numerical computation by using physical insight and novel mathematics. His recent work has shown that current models of diffusion over solid surfaces have overlooked non-diffusive mechanisms contributing to surface mobility, which may be significant in surface catalysis. Additionally, his research indicates that surfaces can segregate ions by size, a finding relevant to chemical separations and desalination. Professor Lichter has received notable recognition including the Office of Naval Research Young Investigator Award and the Clemens Herschel Prize for Excellence in Engineering. He holds a Ph.D. in Mechanical Engineering from MIT, an M.S. in Aerospace Engineering from MIT, and a B.A. in Engineering and Applied Physics from Harvard University. He teaches courses on Modeling Energy in Society, Molecular Motors in Biology, and Nonlinear Dynamics, applying interdisciplinary techniques to explore energy systems, protein dynamics, and complex equations across various scientific applications.

Research topics

• Computer Science
• Physics
• Information Retrieval
• Materials science
• Chemical physics
• Thermodynamics
• Composite material
• Chemistry
• Molecular physics
• Mechanics
• Biochemistry
• Atomic physics
• Nanotechnology

Selected publications

• Slip Due to Kink Propagation at the Liquid-Solid Interface

  arXiv (Cornell University) · 2024

  Senior authorCorresponding
  • Materials science
  • Mechanics
  • Composite material

  In Couette flow, the liquid atoms adjacent to a solid substrate may have a finite average tangential velocity relative to the substrate. This so-called slip has been frequently observed. However, the particular molecular-level mechanisms that give rise to liquid slip are poorly understood. It is often assumed that liquid slip occurs by surface diffusion whereby atoms independently move from one substrate equilibrium site to another. We show that under certain conditions, liquid slip is due not to singular independent molecular motion, but to localized nonlinear waves that propagate at speeds that are orders of magnitude greater than the slip velocity at the liquid-solid interface. Using non-equilibrium molecular dynamics simulations, we find the properties of these waves and the conditions under which they are to be expected as the main progenitors of slip. We also provide a theoretical guide to the properties of these nonlinear waves by using an augmented Frenkel-Kontorova model. The new understanding provided by our results may lead to enhanced capabilities of the liquid-solid interface, for heat transfer, mixing, and surface-mediated catalysis.

  PublisherOA PDFDOI

• Slip due to kink propagation at the liquid–solid interface

  Journal of Fluid Mechanics · 2024-11-25

  articleOpen accessSenior authorCorresponding

  In Couette flow, the liquid atoms adjacent to a solid substrate may have a finite average tangential velocity relative to the substrate. This so-called slip has been observed frequently. However, the particular molecular-level mechanisms that give rise to liquid slip are poorly understood. It is often assumed that liquid slip occurs by surface diffusion whereby atoms independently move from one substrate equilibrium site to another. We show that under certain conditions, liquid slip is due not to singular independent molecular motion, but to localized nonlinear waves that propagate at speeds that are orders of magnitude greater than the slip velocity at the liquid–solid interface. Using non-equilibrium molecular dynamics simulations, we find the properties of these waves and the conditions under which they are to be expected as the main progenitors of slip. We also provide a theoretical guide to the properties of these nonlinear waves by using an augmented Frenkel–Kontorova model. The new understanding provided by our results may lead to enhanced capabilities of the liquid–solid interface, for heat transfer, mixing, and surface-mediated catalysis.

  PublisherOA PDFDOI

• Ring Homopolymers Prefer Crumpling into Odd‐Length Segments

  Macromolecular Theory and Simulations · 2022-03-16

  articleOpen accessSenior authorCorresponding

  Abstract By studying the collapse of a simple ring homopolymer devoid of solvent interactions and chemical heterogeneity, it is shown that segments with an odd number of low‐energy dihedral angles are unusually frequent. The prevalence of odd‐size segments is due to the greater decrease in end‐to‐end length as compared with crumpling to even‐size segments. These results suggest that the sizes of some conformational features of polymers may arise, not due to specific chemical interactions, but rather from generic characteristics of polymers.

  PublisherOA PDFDOI

• Kink propagation and solute partitioning in an atomic monolayer on a substrate

  Physical review. E · 2021 · 2 citations

  • Atomic physics
  • Materials science
  • Molecular physics

  When a monolayer of Lennard-Jones atoms is driven by an external force over an atomically spaced lattice, the atoms do not move in the direction of the force. By considering monolayers containing a solvent and two different solutes, we show that the different atomic species follow distinct directions and so partition from one another and from the solvent. The strength of the driving force is chosen so that at any instant, most atoms are stationary while only a small fraction propagates as solitary waves. In this regime, the mean velocity of the layer is due to the nonzero contribution from merely a few atoms. We also present a simple theory, based on the probability that an atom in the monolayer will hop from one equilibrium location to the next, that explains the distinct directions of atomic migration.

  PublisherDOI

• Substrates sort solute from solvent molecules

  APS Division of Fluid Dynamics Meeting Abstracts · 2020

  Senior authorCorresponding
  • Computer Science
  • Chemistry
  • Computer Science
  Publisher

• Thickening Mechanisms of Polyisobutylene in Polyalphaolefin

  Tribology Letters · 2017-11-25 · 10 citations

  articleOpen access
  PublisherOA PDFDOI

• Effect of Molecular-Scale Features on the Polymer Coil Size of Model Viscosity Index Improvers

  Tribology Letters · 2016-03-31 · 29 citations

  article
  PublisherDOI

• Microtubule-Driven Conformational Changes in Platelet Morphogenesis

  Biophysical Journal · 2015-01-01 · 1 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• Thermodynamics of water structural reorganization due to geometric confinement

  APS March Meeting Abstracts · 2015-03-01

  articleSenior author
  Publisher

• Stability and Structure of Nanometer-Thin Perfluoropolyether Films Using Molecular Simulations

  Tribology Letters · 2014-03-12 · 9 citations

  article
  PublisherDOI

Frequent coauthors

• Andrew J. Bernoff

  11 shared

• Ashlie Martini

  11 shared

• Christopher G. Goedde

  DePaul University

  7 shared

• Meihong Sun

  Baylor University

  7 shared

• Alex Roxin

  Centre de Recerca Matemàtica

  6 shared

• Thomas B. Sisan

  Northwestern University

  6 shared

• Mark Weislogel

  5 shared

• Taeil Yi

  Kyungnam University

  4 shared

Awards & honors

• Office of Naval Research Young Investigator Award
• Clemens Herschel Prize for Excellence in Engineering